In general, a transparent conductive layer has been used as an essential component of electrical and electronic devices such as transparent electrodes in various display fields such as a display device for power supply, an electromagnetic shielding layer of home appliance, liquid crystal display (LCD), organic light emitting diode (OLED), field emission display (FED), plasma display panel (PDP), flexible display, and electronic paper, and as a material of the transparent conductive layer, an inorganic oxide conductive materials such as indium-tin oxide (ITO), antimony-tin oxide (ATO), antimony-zinc oxide (AZO), and the like, have been mainly used.
When the above-described materials are used to manufacture a transparent conductive layer by general methods such as a sputtering method, an ion-beam method, a vacuum depositing method, and the like, the transparent conductive layer may have high conductivity and excellent transmittance. However, equipment cost for the vacuum device is large and it is difficult to be mass-produced and size-increased, and in particular, there is a limitation in a transparent board such as a plastic film, requiring a low temperature process.
At the time of deposition by the sputtering process, a composition of the transparent layer is changed in accordance with conditions such as an oxygen partial pressure, temperature, and the like, such that transmittance and resistance of a thin film are rapidly changed.
Therefore, a method of using the transparent conductive layer manufactured by using a wet coating method such as a spin coating, a spray coating, a deposition coating, a printing, or the like, which is appropriate for low cost and mass-production to be coated, and performing a firing process, has been suggested, and for example, Korean Patent Laid-Open Publication No. 1999-011487 discloses a transparent conductive layer using a metal microparticle and a binder, Korean Patent Laid-Open Publication No. 1999-064113 discloses a composition for a transparent conductive layer prepared by adding tin oxide to a hollow carbonized microfiber, and Korean Patent Laid-Open Publication No. 2000-009405 discloses a coating solution for a transparent conductive light selective and absorbing film prepared by adding tin oxide or indium oxide to neodymium oxide. In addition, Japanese Patent No. 2003-213441 discloses a method of preparing a transparent conductive layer forming solution containing metal microparticles such as gold, silver, and the like.
However, in the transparent conductive layer prepared by the above-described method, surface resistance is high, and surface resistance is increased according to time by change in surrounding environment to have time dependency, such that initial conductivity may not be maintained. In addition, since the transmittance is low, there is a limitation as a transparent conductive layer, and productivity is deteriorated due to a number of complicated processes.